The present invention relates to a motor including a rotor adopting a consequent pole type structure.
Japanese Laid-Open Patent Publication No. 4-71342 describes a rotor of a so-called consequent pole type structure that is used in the motor. In such a rotor, a plurality of magnets are arranged along a circumferential direction of a rotor core. Core pole portions functioning as magnetic poles differing from the magnets are arranged between the magnets and formed integrally with the rotor core. The motor including such a rotor reduces the number of magnets in the rotor to one half without lowering performance and is thus advantageous since fewer natural resources are used and costs are reduced.
In a rotor of a consequent pole type structure, magnets that apply a compelling force on the magnetic flux (induction) are mixed with magnetic poles that do not apply a compelling force on the magnetic flux. Thus, there is a tendency for a magnetic imbalance to occur. This may increase vibration caused by the generation of cogging torque and thereby adversely affect the rotational performance. Accordingly, the rotor described in Japanese Laid-Open Patent Publication No. 4-71342 includes a groove extending along the axial direction in the outer surface of each magnet pole portion to suppress biasing of the magnetic flux in the magnet pole portion and reduce the cogging torque. However, the publication does not describe in detail how the groove of the magnet pole portion is set to effectively decrease vibration in the motor. Improvements may be made from this aspect.